This invention relates generally to a tubular device meant to be inserted into an object and imaged with an X-ray source. More particularly, the present invention relates to such a device having an X-ray contrast medium function.
The present invention is especially suited for use in a medical environment such as use in a catheter, an angioscope, a directional atherectomy device, a cannula or the like. It should, however, be appreciated that the subject invention is capable of broader applications and could be used, e.g. in an industrial setting or in any other environment where a tubular device is inserted into an object and needs to be localized by means of X-ray radiation or the like.
Medical radiography is performed using essentially a point source of X-rays whose beams expand, pass through living tissue being investigated and expose an X-ray sensitive emulsion coated on film or expose a fluorescent screen in accordance with the attenuation intensity of the X-rays. A fluoroscope is an instrument for visual observation of the deep structures of a body by means of X-ray. A patient is put into a position such that the portion of the body to be viewed is placed between an X-ray tube and a fluorescent screen. X-rays from the tube pass through the body and project the bones and organs as shadowy images on the screen. A radiopaque medium aids in this process of examination of the body, which is called fluoroscopy.
Various types of catheters such as an angiographic catheter, a urethral catheter, a bronchographic tube or a thoracic catheter have been conventionally used in medicine for indwelling in body cavities. Often, an X-ray contrast medium is mixed partially or entirely in these catheters or employed to circumferentially form a ring mark on the outer surface of the catheters. A doctor inserts the catheter having an X-ray contrast medium into a body cavity while observing an X-ray fluoroscopic image. Fluoroscopically visible tip markers on such catheters permit the longitudinal positioning of the catheters to be monitored as they are inserted into the vascular system of the patient. Such markers typically consist of one or more bands of radiopaque material mounted on the distal end portion of the catheter.
It is also a common practice in the medical field for a physician to insert a cannula through a natural opening in a patient's body, such as the nasal or oral opening or through an incised opening and to advance the cannula to a particular location within the body. In order to properly place these cannulas, and especially their distal tips, within the body so that they will accomplish their intended purpose without injuring the patient's internal tissue, a physician or radiologist typically uses an X-ray photograph or a fluoroscope to examine the location of the cannula within the body. Often a fluoroscope is used to visually monitor the location of the cannula as it is being inserted. Therefore, it is necessary that some portion of the cannula be radiopaque.
However, the X-ray fluoroscopic image of the medical device, such as a catheter or a cannula, is a two dimensional image so that even if a distal end portion of the medical device is rotated along its longitudinal axis, or if the device itself is deviated toward or away from the plane of the fluoroscopic screen, the resultant X-ray fluoroscopic image is substantially the same as that obtained along the intended, i.e. correct, direction. The doctor may then mistakenly believe that the device is correctly directed.
With the advent of intravascular imaging devices such as angioscopy and intravascular ultrasound, it becomes important to know the orientation of the medical device within the vascular lumen. For example, FIG. 1 illustrates an arterial vascular lumen 10 having an interior periphery 12 on which is located a plaque 14. A medical device 20 having a distal end 22 is inserted into the vascular lumen. If one were to visualize the abnormal structure or plaque 14 as being located at the twelve o'clock position 24 of the medical device, one has no sure way of knowing where the 12 o'clock position is in relation to the planar radiograph shown in FIG. 1B. That is, the fluoroscope 30 has a flat screen 32. Therefore, the abnormal structure 14 may be at position A or at position B as seen by the planar radiograph or outside of the plane represented by the X-Y coordinate, i.e. at position C.
This becomes an important issue when one wants to direct specific therapy at the structure which therapy frequently requires a different device, for example, a directional atherectomy device or directed laser beams. The operator, therefore, has to guide this device to the position on the fluoroscopic image and then rotationally orient the device so that the twelve o'clock position of the device is pointed at the location C of the vessel. This task is complicated by the size of the devices in question. The total diameter of the medical device may be no more than 1 or 2 millimeters and the fluoroscopic resolution of most radiographic equipment is at best 1/2 to 1 millimeter. Therefore, it is very difficult for a surgeon to correctly orient a medical device with the radiopaque markers available at present.
Accordingly, it has been considered desirable to develop a new and improved tubular device meant to be inserted into an object and imaged with an X-ray source which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.